The present invention relates to a polyamide resin. More particularly, the invention relates to a polyamide resin which has low water absorption, is excellent in moldability, mechanical strength and heat resistance and is favorably used for electric or electronic parts, a polyamide resin composition using the polyamide resin, and an electric or electronic part comprising the polyamide resin composition.
Resins used as materials of automobile parts and electric or electronic parts need to be excellent in heat resistance, moldability and low water absorption. Therefore, various aromatic polyamides having relatively high heat resistance and low water absorption have been heretofore proposed.
For example, the present applicant has proposed, in Japanese Patent Laid-Open Publication No. 281532/1991, a polyamide resin composition comprising an aromatic polyamide and a fibrous filler, wherein the aromatic polyamide comprises (a) dicarboxylic acid component units consisting of 52 to 58% by mol of terepthalic acid component units and 48 to 42% by mol of aliphatic dicarboxylic acid component units and (b) diamine component units consisting of aliphatic alkylenediamine component units and/or alicyclic alkylenediamine component units and has an intrinsic viscosity [xcex7], as measured in concentrated sulfuric acid at 30xc2x0 C., of 0.5 to 3.0 dl/g. This polyamide resin composition is relatively excellent in heat resistance, low water absorption, mechanical strength and impact resistance.
In Japanese Patent No. 2641788, a crystalline copolyamide having hexamethylene terephthalamide units and having a relative viscosity (xcex7r) of 1.5 to 5.0 is described. More specifically, a copolyamide having a molar ratio (6T/6) of hexamethylene terephthalamide units to caproamide units of 70/30 and a copolyamide having a molar ratio (6T/66) of hexamethylene terephthalamide units to hexamethylene adipamide units of 55/45 are described.
In Japanese Patent Laid-Open Publication No. 1826/1996, an automobile part comprising a material obtained by adding an inorganic filler and a flame retarder to a crystalline terpolymer comprising (A) an equimolar salt (66 salt) of hexamethylene diamine and adipic acid, (B) an equimolar salt (6T salt) of hexamethylene diamine and terephthalic acid and (C) nylon 11 or nylon 12 is described. More specifically, a molded product of a resin composition using a terpolymer having a 6T/66/12 molar ratio of 50/50/3 or 60/40/5 is described.
In Japanese Patent Publication No. 56576/1991, a polyamide having high heat resistance and low water absorption is disclosed. As a result of studies by the present inventor, however, this polyamide has low flowability in the molding process and does not have sufficient moldability when it is molded into a complicated shape.
In recent years, a xe2x80x9clead-free solderxe2x80x9d which uses no lead has been used as a solder for electric products from the viewpoint of environmental protection. The reflow temperature of the lead-free solder tends to be higher than that of an eutectic crystal solder of lead and tin which has been heretofore widely used. Therefore, when the lead-free solder is used to connect a printed wiring board with an electric or electronic part, the resin for forming the electric or electronic part needs to have higher heat resistance, particularly that in the solder reflow process.
In case of reflow mounting, the electric or electronic part may suffer occurrence of blister on its surface if the water absorption of the part is high. Therefore, a resin having lower water absorption is desired.
In recent years, further, miniaturization and higher precision of electric or electronic parts tend to be desired. For the electric or electronic parts, therefore, a resin composition of better moldability, which is capable of being injection molded into precision parts and exhibits excellent flowability in the molding process, is desired.
Under such circumstances, particularly for electric or electronic parts, there has been intensely desired development of a polyamide resin and a polyamide resin composition each of which is superior to the above-mentioned conventional polyamide resins in the heat resistance, low water absorption, mechanical strength and moldability.
The present invention is intended to solve such problems as described above, and it is an object of the invention to provide a polyamide resin and a polyamide resin composition each of which has low water absorption, is excellent in moldability, mechanical strength and heat resistance and is suitably used for electric or electronic parts.
The present invention is a polyamide resin composition having a solder reflow heat-resistant temperature of not lower than 250xc2x0 C.
The present invention is also a flame-retardant polyamide resin composition comprising a polyamide resin, a flame retarder, a flame retarder assistant and a fibrous reinforcement and having a solder reflow heat-resistant temperature of not lower than 250xc2x0 C.
The polyamide resin composition according to the invention is a composition comprising a polyamide resin and having a solder reflow heat-resistant temperature of not lower than 250xc2x0 C., wherein the polyamide resin comprises:
(A) dicarboxylic acid component units comprising:
(A1) aromatic dicarboxylic acid component units in amounts of not less than 60% by mol and less than 70% by mol, and
(A2) aliphatic dicarboxylic acid component units and/or alicyclic dicarboxylic acid component units in amounts of more than 30% by mol and not more than 40% by mol, and
(B) diamine component units comprising aliphatic alkylenediamine component units and/or alicyclic alkylenediamine component units,
said polyamide resin having an intrinsic viscosity, as measured by the use of concentrated sulfuric acid at 25xc2x0 C., of not less than 0.5 dl/g and not more than 3.0 dl/g.
The polyamide resin preferably comprises:
(a) dicarboxylic acid component units comprising 61 to 64% by mol of aromatic dicarboxylic acid component units and 39 to 36% by mol of aliphatic dicarboxylic acid component units, and
(b) diamine component units comprising aliphatic alkylenediamine component units and/or alicyclic alkylenediamine component units,
and preferably has an intrinsic viscosity [xcex7], as measured in concentrated sulfuric acid at 25xc2x0 C., of not less than 0.7 dl/g and not more than 1.2 dl/g.
In the polyamide resin of the invention, the aromatic dicarboxylic acid component units are also preferably terephthalic acid component units and/or isophthalic acid component units.
The polyamide resin composition of the invention comprises:
the above-mentioned polyamide resin, and
at least one substance selected from the group consisting of a fibrous reinforcement, a modified polymer, an ionomer resin, an aliphatic polyamide and a flame retarder.
The polyamide resin composition of the invention preferably is a polyamide resin composition containing the fibrous reinforcement in an amount of 5 to 250 parts by weight based on 100 parts by weight of the polyamide resin, or a polyamide resin composition containing the modified polymer and/or the ionomer resin in an amount of 1 to 70 parts by weight based on 100 parts by weight of the polyamide resin, or a polyamide resin composition containing the aliphatic polyamide in an amount of 1 to 70 parts by weight based on 100 parts by weight of the polyamide resin. The polyamide resin composition of the invention also preferably comprises the polyamide resin and two or more substances selected from the group consisting of a fibrous reinforcement, a modified polymer, an ionomer resin, an aliphatic polyamide, 2 to 100 parts by weight of a flame retarder based on 100 parts by weight of the polyamide resin, and 2 to 20 parts by weight of a flame retarder assistant based on 100 parts by weight of the polyamide resin.
The electric or electronic part according to the present invention comprises the polyamide resin composition.